1. Field of the Invention
The present invention relates to an alignment system for lasers and more particularly to a alignment system for co-aligning multiple time-multiplexed pulsed laser beams to a single reference point in real time.
2. Description of the Prior Art
Alignment systems for aligning the output beams of lasers are generally known in the art. Examples of such alignment systems are disclosed in U.S Pat. Nos. 4,146,329; 4,626,649; 4,724,298; 4,855,564; 4,982,078; and 4,941,082, hereby incorporated by reference. Such alignment systems normally sample the laser beam in order to develop an error signal. The error signal is used to drive, for example, an alignment mirror, disposed in the optical path of the laser for correcting the spatial position of the laser beam. Various methods are known for developing an error signal. For example, U.S. Pat. No. 4,982,078 utilizes a quadrant detector. The quadrant detector is disposed in the beam path. The signals from the quadrant detector are used to develop error signals.
Systems are also known for aligning laser systems which utilize a plurality of lasers. For example, commonly owned U.S. Pat. No. 4,847,479 discloses an optical communication system which utilizes multiple laser output beam, which are wavelength multiplexed by way of a diffraction grating. In order to compensate for wavelength drift and mechanical alignment drift, the ""479 patent discloses an auto-alignment system. In particular, the system samples the output beam and utilizes a quadrant detector for detecting the mechanical alignment drift in the lasers. Although each laser beam is identifiable by its wavelength, the wavelength may be too close in frequency to permit the use of filtering to identify the beams. As such, a tracer signal is generated for each laser beam. A tracer signal may be formed by superimposing low frequency sine waves on each laser beam. Either different frequencies may be used for the tracer frequencies for each laser beam or the same frequency used at pre-selected times in a time multiplexed manner.
Laser systems are also known in which pulsed laser output beams are time multiplexed and directed to a single spatial reference point. There are no known alignment systems for aligning laser pulses from multiple lasers and co-aligning such pulses to a signal spatial target in real time. Thus, there exists a need for an alignment system for co-alignment of multiple time multiplexed pulsed laser beams directed to a single spatial target in real time.
The present invention relates to an alignment system for co-aligning multiple laser beams to a single spatial reference point in real time. The alignment system includes a beam sampler for sampling the multiple pulsed laser beams. The sampled laser beams are directed onto a quadrant photodetector or quad cell. The output signals from the quad cell are directed to a detector signal integration circuit which develops error signals for driving tip-tilt mirrors in the beam path of the multiple lasers. The system includes a gate, reset and pulse ID generator for generating pulse trigger signals for each of the multiple lasers and signals for correlating the detector signals with the laser that produced the signal. Accordingly, a system is provided for a time multiplexed multiple laser system which automatically co-aligns the output beams from each of the lasers to a single spatial reference point in real time.